374 
ON THE ACARUS, 
glisten. More forward, and somewhere about the place which 
in most animals is occupied by the shoulder-blade, is found a 
moderately long stiff hair. On each side of the body, about 
the commencement of the hinder third part, are placed two other 
hairs, one of which is very short, and the other about as long as 
the body is broad. The under part of the body shews the same 
elevated and depressed lines as the back, but in different direc¬ 
tions ; and also at the fore end of the body are seen two reddish 
lines on each side, one pair between the head and the first fore 
foot on each side; and the others commencing between the tw'o 
fore feet, and about the middle of the body, and continuing on 
towards the hinder parts : these two lines appear to be united 
about their middle by a cross band. 
Raspail, who first described these appearances on the belly, 
recommends that, in order to make them more visible, the mites 
should be laid in concentrated sulphuric acid, by which means 
the albuminous portion of the animal resembling the white of 
an egg would be got rid of, and the remainder rendered trans¬ 
parent. By the help of a good microscope, however, these lines 
can be seen without the aid of the acid. 
The head {a) is placed on the middle of the front edge of the 
coat of mail of the trunk, but is not covered by it. It possesses 
a tapering trunk-like form, and the point of it is directed down¬ 
wards. The length of the head is about one-third of that of the 
body, and its thickness is a little more than are the fore feet at 
their commencement. The construction of the mouth is not yet 
satisfactorily known; it appears, however (so far as I have been 
able to discover by often repeated microscopical observations), 
that here are two distinct kinds of apparatus, namely, one for 
piercing through the skin, and the other for sucking up the 
nourishment. 
For the latter purpose there is on the under side of the head, 
and about the place usually occupied by the under lip, a round 
trunk, thickened towards the body, the end of which is quite 
smooth, and furnished in the middle with a little hollow. This 
is slightly directed downwards; the animal can, however, move 
it at will in a moderate degree on all sides, and also shorten it 
a little. 
. For piercing through the skin, we find above this trunk, and 
resembling a cleft upper lip, two horiaontal spears lying near to 
one another, formed of a horny substance, and something like 
the points of the blades of a pair of scissors. The animal can 
open them nearly to the width of its whole head, and then bring 
them again side by side, in which latter position they appear to 
be but one body; and it is only by means of the little furrow in 
